Communication system

ABSTRACT

The invention relates inter alia to a method of operating a communication system (10). Each communication node (11, 12, 13, 14) of the communication system (10) preferably tracks a successful reception of data signals (D) and requests a switch and/or switches from a currently used communication channel (C1) to another communication channel (C2-C6) in case that no successful receptions were made within a given maximum time interval.

The invention relates to communication systems, communication nodes andmethods of operating communication systems.

BACKGROUND OF THE INVENTION

German Patent Application DE 10 2012 206 529 A1 discloses a method ofoperating a token-ring system where communication nodes send signals toallocated upstream communication nodes and receive signals fromallocated downstream communication nodes.

OBJECTIVE OF THE PRESENT INVENTION

An objective of the present invention is to provide a method whichallows operating a communication systems in a very reliable way.

A further objective of the present invention is to provide acommunication system and a communication node that can be operated in avery reliable way.

BRIEF SUMMARY OF THE INVENTION

An embodiment of the invention relates to a method of operating acommunication system, wherein each communication node of thecommunication system tracks a successful reception of data signals andrequests a switch and/or switches from a currently used communicationchannel to another communication channel in case that no successfulreceptions were made within a given maximum time interval.

An advantage of this embodiment of the invention is that an interruptionof a presently used communication channel can be detected very quickly.As soon as a communication node becomes aware that an expected datasignal has not been received, a switch to an alternative communicationchannel may be initiated immediately. Therefore, in case of aninterruption of the actually used communication channel, the time spanin which the communication nodes remain unconnected, is significantlyreduced compared to communication systems which are presently known.

There are various known methods for establishing whether a reception ofdata signals was successful or not. For instance, reliable methods aredescribed in:

-   -   “Wireless Communication Protocols and Resource Optimization for        Distributed Control of Power Networks”(Muhammad Tahir,        Dissertation, University of Illinois, Chicago, UMI Microform        Number 3345496, pages 62-64),    -   “NETWORKING 2002. Networking Technologies, Services, and        Protocols; Performance of Computer and Communication Networks;        Mobile and Wireless Communications” (Second International        IFIP-TC6 Networking Conference, Pisa, Italy, May 19-24, 2002        Proceedings; Enrico Gregori, Marco Conti, Andrew T. Cambell, Guy        Omidyar, Moshe Zukerman; pages 1010-1012),    -   “Wireless Communications” (T L Singal, Tata McGraw-Hill        Education, 2010, pages 291-292),    -   “Modeling and Tools for Network Simulation” (Klaus Wehrle, Mesut        Günes, James Gross; Springer Science & Business Media,        22.09.2010, pages 250-251),    -   “Ad Hoc and Sensor Networks” (Yi Pan, Yang Xiao, Nova        Publishers, 2006, pages 95-97), and    -   U.S. Pat. No. 8,533,554 B2

Preferably a reception of a data signal is deemed to be successful ifthe receiving entity is able to detect the data signal, decode the datasignal, and proof the correctness of the data signal by deriving a firstcheck value from the data signal and comparing it to a second checkvalue that is enclosed in the received data signal (e.g., a cyclicredundancy check (CRC) value).

According to a preferred embodiment, all communication nodes communicatedirectly with each other on the same channel. An advantage of thisembodiment is that the communication system does not require any centralstation or central node, which handles the communication and—in case ofa failure—would cause a shut down of the entire system. In other words,the communication system can be self-organized with respect to itsmember nodes. Even if one or more nodes fail the other nodes maycontinue their communication.

In case that one or more of the communication nodes fail to makesuccessful receptions within the given maximum time interval on theactual channel, the respective communication nodes send a broadcastsignal to all other nodes in order to request the switch from thecurrently used communication channel to another communication channel.

The broadcast signal is preferably sent on the same channel as theactually used communication channel and/or on a new channel according toa channel sequence that defines the order in which communicationchannels are switched.

According to a preferred embodiment, at least one communication node,preferably each communication node, of the communication system storesusability information with respect to the communication channels thatcan be used by the communication system.

At least one communication node, preferably each communication node, ofthe communication system preferably evaluates stored usabilityinformation and determines a channel sequence that defines the order inwhich communication channels are switched in case that the currentlyused communication channel is interrupted or fails to provide the givenminimum communication quality.

At least one communication node, preferably each communication node, mayregularly scan the communication channels of the communication system inorder to determine the current usability of the communication channelsand to update stored usability information.

At least one communication node, preferably each communication node,preferably measures the electromagnetic radiation on each of thecurrently unused communication channels and determines the currentusability of the communication channels based on the measurement values.

At least one communication node, preferably each communication node,preferably sends data signals to at least one other communication nodeof the communication system and receives data signals from at least oneother communication node of the communication system duringcommunication time slots and scans the communication channels at timesoutside of the communication time slots.

At least one communication node, preferably each communication node,preferably informs at least one other communication node aboutcommunication channels that are usable according to its stored usabilityinformation.

At least one communication node, preferably each communication node,preferably informs at least one other communication node aboutcommunication channels that are unusable according to its storedusability information.

According to a preferred embodiment each of the communication nodes ofthe communication system receives usability information or parts thereofstored by at least one other communication node and uses the receivedinformation to update or amend its stored usability information, andeach communication node of the communication system sends its storedusability information or parts thereof to at least one othercommunication node of the communication system in order to allow theother communication node to update or amend the stored usabilityinformation.

The communication system preferably forms a token-ring system whereineach communication node directly or indirectly—i.e. via one or moreother communication nodes that function as relay nodes—sends datasignals to an allocated downstream communication node and receives datasignals from an allocated upstream communication node.

In a further preferred embodiment, each communication node receivesusability information or parts thereof from the respective upstream nodeand uses the received information to update or amend its storedusability information, and each communication node sends its storedusability information or parts thereof to the respective downstream nodein order to allow the downstream node to update the stored usabilityinformation.

In a further preferred embodiment, the data signals comprise datapackets.

The communication node preferably sends a broadcast signal to request achange of the communication channel if the communication node does notreceive an expected data signal from the allocated upstreamcommunication node within a given maximum time interval.

A further embodiment of the invention relates to a communication nodefor a communication system. The communication node is preferably capableof communicating on the basis of any of a plurality of communicationchannels. Further, the communication node is preferably configured tostore usability information regarding the communication channels, and toswitch and/or request a switch from a currently used communicationchannel to another communication channel in case that the currently usedcommunication channel is interrupted or fails to provide a given minimumcommunication quality.

The communication node is preferably configured to communicate directlywith any or all of the other nodes of the communication system on thebasis of the same communication channel used by the other nodes duringsuccessful reception of data signals. An advantage of this embodiment isthat the communication system does not require any central station orcentral node, which handles the communication and—in case of afailure—would cause a shut down of the entire system. The communicationsystem can therefore be self-organized with respect to its member nodes.Even if one or more nodes fail the other nodes may continue theircommunication.

The communication node may be further configured to send a broadcastsignal to all other nodes in order to request the switch from acurrently used communication channel to another communication channel incase that no successful receptions were made within a given maximum timeinterval.

The communication node preferably comprises a processor unit and amemory that stores usability information regarding each of thecommunication channels. The memory may further store a control programwhich—after activation—programs the processor to switch and/or request aswitch from a currently used communication channel to anothercommunication channel in case that the currently used communicationchannel is interrupted or fails to provide a given minimum communicationquality. The memory may further comprise a software module, hereinafteralso referred to as channel sequence software module, that defines agiven scheme to determine a channel sequence based on the usabilityinformation.

A further embodiment of the invention relates to a communication system.The communication system preferably comprises two or more communicationnodes as described above.

The communication system is preferably a token-ring system and thecommunication nodes are preferably broadcast-type communication nodes.

The communication nodes of the communication system are preferablyconfigured to communicate directly with any or all of the other nodes ofthe communication system on the basis of the same communication channelthat is used by the other nodes during successful reception of datasignals. An advantage of this embodiment is that the communicationsystem does not require any central station or central node, whichhandles the communication and—in case of a failure—would cause a shutdown of the entire system. The communication system can beself-organized with respect to its member nodes and the choice of theactual communication channel. Even if one or more nodes fail the othernodes may continue their communication.

The communication nodes may be further configured to send a broadcastsignal to all other nodes in order to request the switch from acurrently used communication channel to another communication channel incase that no successful receptions were made within a given maximum timeinterval.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above-recited and other advantagesof the invention are obtained will be readily understood, a moreparticular description of the invention briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the invention and are therefore notto be considered to be limiting of its scope, the invention will bedescribed and explained with additional specificity and detail by theuse of the accompanying drawings in which

FIG. 1 shows an exemplary embodiment of a communication system accordingto the present invention and

FIG. 2 shows an exemplary embodiment of a communication node accordingto the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment of the present invention will be bestunderstood by reference to the drawings. It will be readily understoodthat the present invention, as generally described and illustrated inthe figures herein, could vary in a wide range. Thus, the following moredetailed description of the exemplary embodiments of the presentinvention, as represented in the figures, is not intended to limit thescope of the invention, as claimed, but is merely representative ofpresently preferred embodiments of the invention.

FIG. 1 shows an exemplary embodiment of a communication system 10according to the present invention. The communication system 10comprises a plurality of broadcast- type communication nodes 11, 12, 13,and 14.

The communication system 10 forms a token-ring system wherein eachcommunication node directly or indirectly—i.e. via one or more othercommunication nodes—sends data signals D to an allocated downstreamcommunication node and receives data signals D from an allocatedupstream communication node. The data signals D are illustrated byarrows in FIG. 1. The arrows' directions indicate the direction of thecommunication and thus define for each communication node which of theother communication nodes is the respective upstream node and therespective downstream node.

In FIG. 1, it is assumed that communication nodes 11, 12, 13 and 14presently use a communication channel C1.

FIG. 2 shows an exemplary embodiment of a communication node 100 thatcan form any of the communication nodes 11, 12, 13 or 14 in thecommunication system 10 of FIG. 1.

The communication node 100 comprises a transceiver 110 capable oftransmitting and receiving electromagnetic radiation, a processor unit120 and a memory 130. The memory 130 stores a control program CP thatallows the processor unit 120 to operate as explained further below.

The memory 130 also stores a usability table UT that contains usabilityinformation regarding each communication channel that can be used by thecommunication node 100. For example, the communication node 100 may beconfigured to communicate on any of six given communication channelsC1-C6. In this case, the usability table UT comprises usabilityinformation UI1, UI2, UI3, UI4, UI5 and UI6 for each of the sixcommunication channels C1-C6, respectively.

Each usability information UI1, UI2, UI3, UI4, UI5 and UI6 at leastindicates whether or not the respective communication channel C1-C6 canpresently be used or not. For instance, a binary information “1” mayindicate that the respective communication channel can presently beused, and a binary information “0” may indicate that the respectivecommunication channel cannot be used. Of course, the assignment of thebinary information “1” and “0” might also be inverse.

Referring again to FIG. 1, the communication nodes 11, 12, 13 and 14 mayoperate as follows:

Each communication node 11, 12, 13 and 14 tracks the successfulreception of data signals D that are transmitted on the presently usedcommunication channel, e. g communication channel C1. In case that datasignals D are received on time, i.e. within a given maximum timeinterval, the communication nodes 11, 12, 13 and 14 continue tocommunicate on this communication channel C1.

In order to prepare for a situation where the presently usedcommunication channel C1 is interrupted or disturbed, the communicationnodes 11, 12, 13 and 14 regularly scan all of the other fivecommunication channels C2-C6 of the communication system 10 anddetermine the current usability of the other communication channelsC2-C6.

During the scanning procedure, the communication nodes 11, 12, 13 and 14may measure the electromagnetic radiation P(C) on each of the currentlyunused communication channels C2-C6 and evaluate the measurement resultsP(C) for each communication channel. For instance, in case of afrequency domain multiplexing system P(C) can be obtained by using thefollowing formula :

P(C)=∫_(f min((C)) ^(f max(C)) P(f)df

wherein C designates the respective communication channel C2, C3, C4, C5or C6, fmax(C) the upper end of the frequency band of the respectivecommunication channel, fmin(C) die lower end of the frequency band ofthe respective communication channel, and P(f) the radiation density.

In case of a time domain multiplexing system, P(C) can be obtained byusing the following formula:

P(C)=∫_(t min(C)) ^(t max(C)) P(t)dt

wherein C designates the respective communication channel C2, C3, C4, C5or C6, tmax(C) the end of the time slot assignment of the respectivecommunication channel, tmin(C) the beginning of the time slot assignmentof the respective communication channel, and P(t) the radiation density.

In case of multiplexing systems that divide the channels in otherdomains (e.g. space, code, etc), P(C) can be obtained accordingly.

Preferably, a communication channel is deemed to be usable forcommunication if the electromagnetic radiation on the respectivecommunication channel is below a given threshold Pmax. Accordingly, acommunication channel is preferably deemed to be unusable forcommunication if the electromagnetic radiation on the respectivecommunication channel exceeds the given threshold Pmax:

P(C)>Pmax⇒UI(C)=“0” (communication channel unusable)

P(C)<Pmax⇒UI(C)=“1” (communication channel usable)

Based on the evaluation of the measurement results, the usabilityinformation UI1-UI6 stored in memory 130 (see FIG. 2) can be updated.

In FIG. 1, the scanning of the other communication channels

C2-C6 is illustrated with respect to communication node 11, only.

In order to regularly update the stored usability information, thecommunication nodes 11, 12, 13 and 14 preferably scan the communicationchannels C2-C6 on a regular basis. For instance, the communication nodesmay scan the communication channels C2-C6 during all time slots wherethey do not expect the reception of data signals D from othercommunication nodes.

Furthermore, each communication node 11, 12, 13 and 14 may evaluate thestored usability information in order to determine a channel sequencethat defines the order in which communication channels are planned to beswitched in case that the currently used communication channel isinterrupted or fails to provide a given minimum communication quality.

Assuming for instance a situation where the communication channel C1 isthe presently used communication channel and the usability tables UTstored in the memory 130 of the communication nodes 11, 12, 13 and 14contain the following usability information:

usability communication channel information UI(C) priority C1 1 1 C2 1 2C3 0 3 C4 1 4 C5 0 5 C6 1 6

According to the usability table UT above, the communication channelsC2, C4 and C6 are presently usable and the communication channels C3 andC5 are presently unusable. Based on these table entries, each of thecommunication nodes 11, 12, 13 and 14 may determine a channel sequence,for instance the channel sequence C2-C4-C6, which can be used forselecting a new communication channel in case that the presently usedcommunication channel C1 is interrupted.

The channel sequence is preferably determined based on a given schemethat is applied by all communication nodes 11, 12, 13 and 14 in order toguarantee that all communication nodes determine the channel sequence inthe same way and obtain the same result. The given scheme may beimplemented in a software module CSSM (“channel sequence softwaremodule”), which is stored in the memory 130 (see FIG. 2) and responsiblefor determining the channel sequence based on the table entries of theusability table UT.

The given scheme may be based on a priority that is defined for eachcommunication channel, e.g. as indicated in the exemplary table above.The priorities may define for instance that communication channel C2 ispreferred over communication channel C4, and communication channel C4 ispreferred over communication channel C6: Therefore, in the examplepresented above, the channel sequence C2-C4-C6 results.

In order to avoid that usability information stored in the memories ofthe communication nodes 11-14 differ and therefore differing channelsequences might be generated, the communication nodes 11-14 preferablyexchange their stored usability information or parts thereof and usereceived information to update or amend its stored usabilityinformation.

If for instance the communication node 13 stores the usabilityinformation UI4=“0” and all the other communication nodes 11, 12, and 14store the usability information UI4=“1” (as indicated above in thetable), the other communication nodes 11, 12, and 14 preferably updatetheir usability table by downgrading the usability information UI4 toUI4=“0”, because a communication on communication channel C4 would notbe possible for communication node 13:

usability communication channel information UI(C) priority C1 1 1 C2 1 2C3 0 3 C4 0 4 C5 0 5 C6 1 6

The exchange of usability information between the communication nodesmakes sure that all communication nodes refer to the same usabilitytable when they determine their channel sequence.

With respect to the updated usability table above, for instance, thechannel sequence C2-C6 would be determined because communication channelC2 is preferred over communication channel C6. Accordingly, if any ofthe communication nodes does not receive data signals D within the givenmaximum time interval it will request a switch and/or will switch fromthe currently used communication channel C1 to the new communicationchannel C2. If, for whatever reason, the communication fails on channelC2, channel C6 can be tried thereafter.

1. Method of operating a communication system (10), characterized inthat each communication node (11, 12, 13, 14) of the communicationsystem (10) tracks a successful reception of data signals (D) andrequests a switch and/or switches from a currently used communicationchannel (C1) to another communication channel (C2-C6) in case that nosuccessful receptions were made within a given maximum time interval. 2.Method of claim 1 wherein during successful reception of data signals,all communication nodes (11, 12, 13, 14) directly communicate with eachother on the same channel, and in case that one or more of thecommunication nodes (11, 12, 13, 14) fail to make successful receptionswithin the given maximum time interval on the actual channel, therespective communication nodes (11, 12, 13, 14) send a broadcast signalto all other nodes in order to request the switch from the currentlyused communication channel (C1) to another communication channel(C2-C6).
 3. Method of claim 2 wherein at least one communication node,preferably each communication node (11, 12, 13, 14), of thecommunication system (10) stores usability information (UI1-UI6) withrespect to the communication channels (C1-C6) that can be used by thecommunication system (10).
 4. Method of claim 3 wherein at least onecommunication node, preferably each communication node (11, 12, 13, 14),of the communication system (10) evaluates the stored usabilityinformation (UI1-UI6) and determines a channel sequence that defines theorder in which communication channels (C1-C6) are switched in case thatthe currently used communication channel (C1-C6) is interrupted or failsto provide the given minimum communication quality.
 5. Method of claim 4wherein at least one communication node, preferably each communicationnode (11, 12, 13, 14), regularly scans the communication channels(C1-C6) of the communication system (10) in order to determine thecurrent usability of the communication channels (C1-C6) and to updatethe stored usability information (UI1-UI6).
 6. Method of claim 4 whereinat least one communication node, preferably each communication node (11,12, 13, 14), measures the electromagnetic radiation on each of thecurrently unused communication channels (C2-C6) and determines thecurrent usability of the communication channels (C2-C6) based on themeasurement values.
 7. Method of claim 5 wherein at least onecommunication node, preferably each communication node (11, 12, 13, 14),sends data signals (D) to at least one other communication node (11, 12,13, 14) of the communication system (10) and receives data signals (D)from at least one other communication node (11, 12, 13, 14) of thecommunication system (10) during communication time slots and scans thecommunication channels (C1-C6) at times outside of the communicationtime slots.
 8. Method of claim 3 wherein at least one communicationnode, preferably each communication node (11, 12, 13, 14), informs atleast one other communication node (11, 12, 13, 14) about communicationchannels (C1-C6) that are usable according to its stored usabilityinformation (UI1-UI6).
 9. Method of claim 3 wherein at least onecommunication node, preferably each communication node (11, 12, 13, 14),informs at least one other communication node (11, 12, 13, 14) aboutcommunication channels (C1-C6) that are unusable according to its storedusability information (UI1-UI6).
 10. Method of claim 3 wherein each ofthe communication nodes of the communication system (10) receivesusability information (UI1-UI6) or parts thereof stored by at least oneother communication node (11, 12, 13, 14) and uses the receivedinformation (UI1-UI6) to update or amend its stored usabilityinformation (UI1-UI6), and each communication node (11, 12, 13, 14) ofthe communication system (10) sends its stored usability information(UI1-UI6) or parts thereof to at least one other communication node (11,12, 13, 14) of the communication system (10) in order to allow the othercommunication node (11, 12, 13, 14) to update or amend the storedusability information (UI1-UI6).
 11. Method of claim 1 wherein thecommunication system (10) forms a token-ring system wherein eachcommunication node (11, 12, 13, 14) directly or indirectly—i.e. via oneor more other communication nodes that function as relay nodes—sendsdata signals (D) to an allocated downstream communication node (11, 12,13, 14) and receives data signals (D) from an allocated upstreamcommunication node (11, 12, 13, 14).
 12. Method of claim 11 wherein eachcommunication node (11, 12, 13, 14) receives usability information(UI1-UI6) or parts thereof from the respective upstream node (11, 12,13, 14) and uses the received information (UI1-UI6) to update or amendits stored usability information (UI1-UI6), and each communication node(11, 12, 13, 14) sends its stored usability information (UI1-UI6) orparts thereof to the respective downstream node (11, 12, 13, 14) inorder to allow the downstream node (11, 12, 13, 14) to update the storedusability information (UI1-UI6).
 13. Method of claim 12 wherein thecommunication node (11, 12, 13, 14) sends a broadcast signal (D) torequest a change of the communication channel (C1-C6) if thecommunication node (11, 12, 13, 14) does not receive an expected datasignal (D) from the allocated upstream communication node (11, 12, 13,14) within a given maximum time interval.
 14. Method of claim 1 whereina reception of a data signal is deemed to be successful if the receivingentity is able to detect the data signal, decode the data signal, andproof the correctness of the data signal by deriving a first check valuefrom the data signal and comparing it to a second check value that isenclosed in the received data signal (e.g., a cyclic redundancy check(CRC) value).
 15. Communication node (11, 12, 13, 14) for acommunication system (10), characterized in that the communication node(11, 12, 13, 14) is capable of communicating on the basis of any of aplurality of communication channels (C1-C6), and the communication node(11, 12, 13, 14) is configured to store usability information (UI1-UI6)regarding the communication channels (C1-C6), and to switch and/orrequest a switch from a currently used communication channel (C1-C6) toanother communication channel (C1-C6) in case that the currently usedcommunication channel (C1-C6) is interrupted or fails to provide a givenminimum communication quality.
 16. Communication node of claim 15wherein the communication node (11, 12, 13, 14) is configured tocommunicate directly with any or all of the other nodes of thecommunication system on the basis of the same communication channel thatis used by the other nodes, during successful reception of data signals,and the communication node (11, 12, 13, 14) is further configured tosend a broadcast signal to all other nodes in order to request theswitch from the currently used communication channel (C1) to anothercommunication channel (C2-C6) in case that no successful receptions weremade within a given maximum time interval.
 17. Communication system(10), characterized in that the communication system (10) comprises twoor more communication nodes according to claim
 15. 18. Communicationsystem of claim 17 wherein all communication nodes (11, 12, 13, 14) areconfigured to communicate directly with each other on the samecommunication channel during successful reception of data signals, andeach communication node (11, 12, 13, 14) is configured to send abroadcast signal to all other nodes in order to request the switch fromthe currently used communication channel (C1) to another communicationchannel (C2-C6) in case that no successful receptions were made within agiven maximum time interval.
 19. Communication system (10) according toclaim 17, characterized in that the communication system (10) istoken-ring system (10) and the communication nodes are broadcast-typecommunication nodes.